Lunar Reference Timescale

TL;DR

This paper reviews the relativistic effects influencing lunar timekeeping and discusses options for establishing a consistent lunar reference timescale aligned with UTC, crucial for future lunar exploration missions.

Contribution

It provides a comprehensive analysis of relativistic effects on lunar timekeeping and proposes potential lunar reference timescales with considerations for their implementation and traceability.

Findings

Relativistic effects cause measurable time shifts on the lunar surface.

Different options for lunar timescales have distinct advantages and drawbacks.

A proposed lunar timescale can be linked to UTC for consistency.

Abstract

Setting up a relativistic lunar reference frame is of a prime importance in the context of future exploration missions to the Moon. If the procedure for building a consistent reference frame within the framework of the general theory of relativity is well established (cf. resolutions B.3 of IAU 2000), there is still some freedom in the choice of the coordinate timescale to be adopted as reference in the lunar region. In this paper, we review the orders of magnitude of the relativistic effects resulting from (i) the gravitational redshift of a clock on the lunar surface and (ii) the time transformations between a clock on the surface of the Moon and a clock on the surface of the Earth. We then discuss possible options for a lunar reference timescale with their advantages and drawbacks, taking note that the solution which is adopted for the Moon shall then be reemployed for Mars and other planets. Finally, we propose possible realizations of the lunar reference timescale as well as its traceability to UTC.